The present invention relates to a constant velocity ball joint. The constant velocity ball joint is a structure capable of transmitting a torque from a drive shaft to a driven shaft crossing the drive shaft at a constant angular velocity. The characteristic feature of the constant velocity ball joint resides in that the maximum joint angle is very large due to the structure of the joint.
The constant velocity ball joint is composed of an outer race provided with a plurality of ball rolling grooves formed in the inner peripheral surface at an axial end thereof, an inner race provided with a plurality of ball rolling grooves formed in the outer peripheral surface at the other axial end thereof, a plurality of balls received by the ball rolling grooves, and a cage adapted to hold these balls at predetermined positions. The centers of the ball rolling grooves formed in the peripheral surfaces of both races are offset by equal distance from the angular center of the joint in both directions so as to control the rotation of the cage and balls to keep the balls always on the bisector plane of the angle formed between the drive and driven shafts to prevent the fluctuation of rotation speed and torque.
However, when an imperfect spherical bearing rotates to resume the parallel posture from a state inclined due to an axial thrust load, a scoop angle and a relief angle are formed at one sphere end of point of contact between the inner and outer spheres to cause a machining action to cut and break the film of grease as the lubricant to hinder the smooth rotation of the bearing.